Domestic cyclonic vacuum cleaners comprise cyclonic separating apparatus for separating dust from the dirty airflow sucked into the vacuum cleaner, before the relatively clean air is then exhausted.
The separating apparatus may incorporate one or more cyclonic separation stages. In the case where more than one separation stages is provided, the separation stages are fluidly connected in series with one another so that the dirty airflow drawn into the separating apparatus passes in turn through each of the separation stages.
If two separation stages are provided, then the first (or ‘primary’) stage may be a low-efficiency stage intended primarily to remove the larger particles from the dirty airflow, and the second (or ‘secondary’) stage may be a higher efficiency stage intended primarily to remove the smaller particles from the airflow which have not been separated by the first stage.
The higher efficiency secondary stage will normally utilize smaller cyclone diameters than the lower efficiency primary stage. This is because a smaller diameter cyclone produces a higher cyclone velocity than a larger diameter cyclone and consequently subjects the dirt particles to a more aggressive centrifugal separating action. This is better for separating out smaller dirt particles.
The secondary stage may be multi-cyclonic comprising a plurality of cyclones arranged in parallel. This has the benefit of reducing the overall pressure drop across the secondary stage, which may otherwise be quite large because of the smaller cyclone diameters used in the secondary stage.
It is unusual for the primary stage to be multi-cyclonic. Instead, a single, large diameter cyclone is typically used for this first stage. However, multi-cyclonic primary stages do exist in the art, in which the first cyclonic separation stage consists of two identical, relatively large-diameter cyclones arranged in parallel with one another and the dirty airflow is divided equally between the two primary cyclones.
It would be advantageous to provide an improved cyclonic vacuum cleaner.